In the coming year, we hope to purify and characterize more fully the gene products of aro H and aro J. We are especially interested in determining how the precursors of tyrosine and phenylalanine may affect the activity of his H gene product in its synthesis of histidine. We shall assay transaminase in other pathways for their ability to transaminate the precursors of tyrosine and phenylalanine. In addition, we are collaborating with Dr. M. Mergeay who has transformed met-mutants of B. subtilis with Streptomyces DNA. Such "transformants" frequently require tyrosine, tryptophan and histidine. We shall repeat these experiments in our laboratory and if they are repeatable we shall attempt to determine the basis for these requirements. This analysis will include the assay for enzyme activity of tyrosine, tryptophan and histidine. The direction of the research will rely heavily on the results of these enzyme assays.